In metallurgical processing, it is often necessary to reheat metal slabs, billets, ingots or the like after initial formation and prior to rolling. The furnace is used to heat the metal uniformly, and by temperature and combustion control, heat the metal in a fixed position on the furnace hearth until it is heated to rolling temperature. A refractory door or doors, depending on the furnace size, are used to retain the heat within the furnace during the reheating step. Usually, such doors hang freely suspended from a superimposed support structure that supports the door and has apparatus for raising or lowering the door as desired. Such doors can normally range in size from four to twenty-five feet in width and from three to about nine feet in height. The furnace opening that these doors cover can range from about three by three feet to twenty five by nine feet. Some furnaces use a single door to cover the furnace opening while others have two or more side-by-side doors to cover the opening.
During use, the reheat furnace door is raised during changing or removing a metal form, generally using a horizontally extending crane or boom. One area of the reheat furnace door that is constant jeopardy of severe damage is the bottom of the door. When this area is hit by the boom end or billet, during changing or removal, the refractory with which the door is lined begins to spall away and the door's life is limited, since soon the total refractory portion must be replaced so as to reduce the risk of warping or total door failure. Even though only a small portion of the refractory lining may be hit by the metal form, heat escaping through the opening formed in the refractory can cause the structural portion of the door to overheat and warp.
It is an object of the present invention to provide a reheat furnace door that, when damage to the bottom portion thereof occurs, can be refurbished without having to remove the entire door from the furnace.